Generally, a liquid crystal display device includes a pair of substrates and a liquid crystal layer enclosed between the substrates. The pair consists of a TFT substrate and a counter substrate. The TFT substrate includes, for example, a plurality of gate lines, a plurality of source lines, a plurality of pixel electrodes, and a plurality of TFTs formed thereon. On the counter substrate, a common electrode shared by the pixel electrodes is formed. The liquid crystal layer is enclosed between the TFT substrate and the counter substrate with a frame-shaped sealing material surrounding the liquid crystal layer.
A pixel region serving as a display region and a picture-frame region provided around the outer periphery of the pixel region and serving as a non-display region are formed on each of the substrates. The picture-frame region of the TFT substrate includes a sealing material formation region and a terminal region provided around the outer periphery of the sealing material formation region. The terminal region includes a plurality of terminals for supplying signals to the pixel region.
Each of the TFT and counter substrates includes an alignment film formed on a surface facing the liquid crystal layer and controlling orientation of liquid crystal molecules contained in the liquid crystal layer. The alignment film is made of a resin film such as a polyimide film, and has a surface subjected to a rubbing treatment.
Each alignment film is formed by applying liquid polyimide on a surface of the TFT substrate or a surface of the counter substrate, and then by curing the applied liquid polyimide by means of baking. The polyimide can be applied by using flexography or ink jet printing, for example.
When the ink jet printing is used to form the alignment film, an alignment film material, such as polyimide, needs to have a relatively low viscosity such that the alignment film material discharged toward and hitting on the substrate spreads sufficiently over the surface of the substrate.
Since the alignment film material with a low viscosity easily spreads on the surface of the substrate, it is likely that the material reaches the picture-frame region which should not include the alignment film. When the alignment film material reaches the terminal region of the picture-frame region, the terminals becomes covered with the resultant alignment film. Consequently, the alignment film which is an insulating film adversely interrupts continuity between the terminals and a circuit chip connected to the terminals.
Patent Documents 1 and 2 propose preventing an alignment film material from spreading excessively by forming a groove structure between a sealing material formation region of the TFT substrate and a pixel region for displaying images. The groove structure receives and stops the alignment film material.
For the purpose of reduction of spreading by wetting of an alignment film material, Patent Document 3 describes a structure in which a water-repellent region is provided on a surface of a TFT substrate, and a structure in which asperities made of the same material as used for forming a wiring layer on the TFT substrate are provided. Being made of the same material as that for the wiring layer, the asperities can be formed by etching at the same time as formation of the wiring layer.
FIG. 19 is a cross-sectional view showing the principle by which the structure described in Patent Document 3 controls spreading by wetting of the alignment film material. As shown in FIG. 19, the asperities 100 include a plurality of projections 102 arranged at predetermined intervals on a glass substrate 101. The projections 102 are made of the same metal film as used for the wiring layer. When a droplet 103 of the alignment film material is dropped on the asperities 100, the droplet 103 is likely to be repelled due to the presence of air layers 104 formed between the droplet 103 and the glass substrate 101. Accordingly, spreading by wetting of the droplet 103 can be controlled.